Legumes are an important foodstuff and are likely to become more so in the future. Those in some of the legume genuses, such as Phaseolus and Soja, are high in protein and provide an inexpensive alternative to animal protein, for the most part lacking only in methionine to provide a balanced diet.
Unfortunately, ingestion of some of the most nutritious and abundant legume genuses can be accompanied by severe flatulence and associated abdominal distress. The effect on individuals varies widely, but with some people it is sufficiently severe that they avoid consumption of these foods entirely.
Quantitative research on the gas-producing properties of legumes commenced in about 1948. Subsequent research has involved work with many of the species in the genuses having the greatest gas-forming tendencies. In general, this work has been aimed at identifying those components of the seed that are responsible for flatulence. One of the significant investigations in this direction was reported by Steggerda, et al., in Soc. for Exper. Biol. and Med., 121, 1966, pp. 1235-9, who separated soybeans into various fractions and determined the flatus production in man with each of these fractions. They found that soybean hulls, fat, water-insoluble polysaccharides, and protein are not associated with flatulence production to any significant degree, and that the flatus-producing factor in soybeans was concentrated primarily in the low molecular weight carbohydrate fraction soluble in water. Research on other legume genuses pointed in the same direction. Compounds specifically identified as being a cause of flatus production are the alpha oligosaccharides, stachyose, raffinose, and verbascose.
The generally accepted explanation of the action of the alpha oligosaccharides in producing flatus is that the enzyme alpha galactosidase is not present in the intestinal tract of mammals. Thus, these compounds are not hydrolyzed and dissolved in the digestive tract so that they can be absorbed. Instead they reach the lower intestine essentially intact. Here anaerobic bacteria ferment these sugars with the resultant production of carbon dioxide and hydrogen, as well as some methane. Thus, these sugars are not only a source of discomfort but constitute a significant loss in nutritional value, since they amount to on the order of 4 percent of the total weight (dry basis) of white beans and 6 percent of soybeans.
Rackis in ACS Symposium Series 15, Sept. 11-12, 1974, pp. 207-221, reported an interesting experiment in which anaerobic cultures isolated from dog colon biopsies were used to treat a group of monosaccharides (glucose, maltose, fructose, galactose) and a group of oligosaccharides (sucrose, raffinose, and stachyose). It was found that the gas produced by all of these compounds (primarily carbon dioxide and hydrogen) was of essentially the same magnitude. Thus, any of these compounds reaching the lower intestine would result in gas formation. However, it is known that ingestion of either the monosaccharides or sucrose in normal quantities does not result in flatus. The significance of these results is that flatus production in the lower intestine may in part be related to solubility. The chemical structure of sucrose as a disaccharide is more similar to that of raffinose and stachyose than it is to the monosaccharides. Yet sucrose and the monosaccharides are highly soluble in water, whereas raffinose and stachyose have a much more limited solubility. High molecular weight polysaccharides, on the other hand, are so nearly insoluble that they may not be susceptible to anaerobic fermentation during the time of passage through the colon.
Having established that the alpha oligosaccharides present in legumes were responsible for flatulence and that the monosaccharide products of their hydrolysis did not cause flatulence, the solution to the problem would seemingly be simple. Various methods of hydrolyzing oligosaccharides have been known for many years. Perhaps the first patent on the subject was issued to Gollmert in 1906 (German Pat. No. 195,972). Gollmert used emulsin and similarly acting enzymes such as kefir lactose. Numerous other enzymes such as invertase, lactose, raffinase, and manninotriase have been reported in the technical literature as having the capability of hydrolyzing raffinose, stachyose, and verbascose.
The oligosaccharides can also be hydrolyzed by chemical means. In addition to inorganic acids such as hydrochloric, some organic acids also have this capability. Matumoto in J. Chem. Soc. Japan, 60, 1939, pp. 1127-48, found that sucrose, raffinose, and stachyose present in the Satsuma orange are easily hydrolyzed by citric acid at a pH of 1.7.
Certain enzyme systems have been used with considerable success to reduce the alpha oligosaccharide content of legumes. Sherba, et al, in U.S. Pat. No. 3,632,346, Ciba Geigy in French Pat. No. 2,137,548, and Sugimoto, et al, in J. Food Sci. 35, 5, 1970, pp. 655-60, have employed carbohydrate enzymes obtained from fungal yeast and bacterial organisms for hydrolysis. It has also been found that legumes themselves contain an alpha galactosidase, and in U.S. Pat. No. 3,876,807 of Wagner, et al, an autolysis process was employed wherein beans were held at 45.degree. to 55.degree. C. for 24 to 48 hours at a pH of 5 to 5.5. By this process the content of stachyose, raffinose, and phytic acid was greatly reduced.
Another approach to reducing the alpha oligosaccharide content of legumes had been extraction. Ethanol has been used. Also, by extensive blanching and soaking with water, and discarding the soak water prior to cooking, the alpha galactosides can be substantially removed, according to A. C. Olsen reporting at the ACS Symposium on Anti-Nutrients and Natural Toxicants in Foods, April 1979.
These simple and logical solutions have not been proven effective, upon testing. Calloway, et al., report in J. Food Sci., 36, 1971, pp. 251-5, on experiments in which various legumes were fed to humans and the quantity of flatus measured. It was found that some reduction in flatus occurred by enzyme treatment and by alcohol extraction, but that flatus was by no means completely eliminated. Products such as tempeh and tofu, from which nearly all carbohydrates have been removed, were found to be essentially non-flatulent.
The foregoing shows that heretofore no method of treatment has proved completely successful in eliminating flatulence and associated indigestibility from beans without removing nearly all of the carbohydrates present. Thus, there is a loss of a potentially nutritious component. Moreover, some of the methods that have been attempted require grinding the beans in the treatment process. Any method or formulation for solving the flatulation problem must not disturb other consumer-accepted bean properties. Such a method or formulation must not alter the texture of the final product. It must avoid emphasizing harsh bitter "off-flavors" inherently present in beans. Finally, to be commercially viable, it must neither significantly increase processing costs nor raw material expense of the final bean products. The present process and formulation meets these objectives.
Legumes pose additional difficulties as well which limit their usefulness. For example, conventional processing of legumes requires that beans be soaked prior to cooking. The soak water leaches out nutrient value from the beans. This nutritional value is routinely discarded because the soak liquid lends a bitter "off" taste to the final product if the legumes are cooked in the soak liquid. Also, with many cooked bean products, it is desirable to present associated sauce or other interstitial fluid having a rich thick consistency. Many legumes, especially soybeans, fail to provide the desired thick sauce with conventional cooking methods. The present invention solves these problems as well.
The present invention employs neutralized enzyme systems found in certain pineapple or papaya materials. Several common cookbooks (for example, Joy of Cooking, Rombaner et al., 1971, p. 261) disclose the addition of normally edible pineapple components--chunks, crushed and slices--to baked bean dishes as garnishes or flavoring components. At no point do these teachings suggest the present deflatulation or comestibility improvement findings nor the use of the present neutralized enzyme systems.